1. Field of the Invention
The present invention relates to a rotary switch and a switching device including such a rotary switch for a hand-held power tool such as a combination hammer drill for producing at least partially rotatable movement of a working tool.
2. Description of the Prior Art
A combination hammer drill includes generally drive means for producing both rotational and percussion movements, which permits switching between different operational modes such as drilling, drilling and chiseling, chisel positioning, and pure chiseling. The switching is effected manually with a mode selection switch which is connected with the hand-held power tool drive. An inadvertent switching from, e.g., a chiseling operational mode, when in accordance with the operational mode, a non-rotatable working tool is used, to a drilling operational mode or a drilling and chiseling operational mode can present a danger for the user.
Generally, the selection of an operational mode is effected with switching sleeves located within the hand-held power tool. The switching sleeves are primarily oriented parallel to the rotational direction of the drive shaft and are linearly displaceable in the hand-held tool housing. The positioning of the switching sleeves results in appropriate formlocking engagements in the area between a tooth gear and the drive shaft. Mostly, two separate switches are provided for drilling and chiseling operational modes for operating at most two separate switching sleeves. For safety reasons, when the hand-held tool has more than two operational mode, dependent on a possible sequence of the operational modes, rather expensive means needs to be provided to insure mutual blocking of separate switching or indexing positions.
A rotary switch for selecting one of several discrete switching or indexing positions, which is determined by a respective angular range, is manually rotated in a respective direction in accordance with a permissible switching sequence over the predetermined angular range. The switching is effected by converting the rotational movement of the rotary switch into other types of movement, e.g., the linear, movement in respective switching positions. The conversion is effected with, e.g, a switching member or special guide means.
German Publication DE 43 02 083A1 discloses a rotary switch for switching between different modes that includes an eccentrically arranged journal engaging in a groove of a linear displaceable switching sleeve.
It is known to provide, in the transitional region between different operational modes, resilient elements for switching between different operational modes. A discrete switching position is determined by a stable condition of a spring-biased elastic element. Thus, U.S. Pat. No. 5,379,848 discloses synchronization of switching by using a spring-biased tooth gear, with the rotary switch being switchable in any other position. The switching of a position is effected by a linear displacement of a switching sleeve into which a journal, which is eccentrically arranged in the rotary switch, engages.
In U.S. Pat. No. 5,992,257, the synchronization of a switching process is effected with a resilient element arranged between two movable parts of the rotary switch. One part is switched manually against a biasing force independent of an internal synchronization condition. The other part is subjected to action of a spring force generated during the internal switching process upon effecting the synchronization.
European Publication EP 0 437 716 discloses a rotary switch for a hand-held tool with three operational modes. The rotary switch includes a switching spring for effecting synchronization. An inadvertent further switching is reliably prevented with a push-button formlockingly engaging in the rotary switch.
An object of the present invention is to provide a single rotary switch for a hand-held power tool for selecting an operational mode of at least three operational modes of the hand-held power tool and with which the operational mode can be selected independent from the instantaneous position of the inner switching means.
Another object of the present invention is to provide a rotary switch for a hand-held tool with more than two operational modes which reliably prevents an inadvertent switching from an actual mode to an adjacent, in the switching sequence, mode of operation.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a rotary switch including a manually operated actuation member rotatable over a predetermined angle for switching from one operational mode to another immediately adjacent operational mode, a rotatable switching member for displacing a switching element of the hand-held power tool and arranged coaxially with the actuation member, an overhanging spring connected with the switching member for joint rotation therewith, and an operating pin connected with the actuation member and arranged eccentrically with respect to its rotational axis for deflecting an arm of the overhanging spring. Thereby the switching member is rotated over a predetermined angle and provides for a predetermined displacement of the switching element necessary for switching from the one operational mode to the other operational mode.
According to the present invention, the eccentrically arranged operating pin transmits a torque from the rotatable actuation member to an overhanging spring, which is preferably formed as a leaf spring and is fixedly connected with the rotatable switching member. The overhanging spring acts as a resilient coupling between the actuation member and the switching member, functioning as a torque-transmitting element of the actuation member and as a torque-receiving member of the switching member. The overhanging spring temporarily stores the torque until a formlockingly engagement of the switching member with the inner switching element in the hand-held power tool takes place.
The self-locking of the actuation member with respect to the hand-held tool housing is advantageously effected by an adequate static friction or by a retaining element, e.g., a spring-biased ball engageable in a recess formed in the actuation member.
Advantageously, the available spring excursion of the overhanging spring is limited by a stop connected with the switching member and limiting the deflection of a spring arm by the operating pin. The stop prevents an unpermissible overturning of the actuation member of the switch. Thereby, the overloading of the spring and the overrotation or overturning toward the next, in the switching sequence, position are reliably prevented. The overturning toward the next position is prevented as a result of the constraint caused the stop which prevents further deflection of the spring by the operating pin.
Advantageously, for each rotational direction of the rotary switch corresponding to a respective operational mode, there is provided an operating pin and/or an overhanging spring. Thereby, the rotary switch is protected from overrotation in both directions, and upon rotation of the rotary switch, only the operating pin and the overhanging spring, which are associated with the specific rotational direction of the rotary switch, cooperate.
Advantageously, there is provided a common spring with two independently deflectable arms, which cooperate with respective operating pins. The spring is advantageously secured, in its middle section, to the switching member for joint rotation therewith.
Advantageously, the point of attachment of the spring is located opposite the operating pin or pins, which provides for a larger spring excursion.
Advantageously, when there are provided several arms and/or operating pins, they occupy, with respect of a set position, when there are provided synchronized switching elements, mirror symmetrical positions. An operating pin can be so arranged that it contacts one or both sides of the overhanging arm of the spring.
A single overhanging arm advantageously is located on the periphery of the plane of symmetry and is biased by one or both operating pins transverse to the plane of the symmetry. With two overhanging arms, they are advantageously extend along chords symmetrically arranged relative to each other, and are biased transverse to the longitudinal extent inward and/or outward by one or two operating pins associated therewith, or by one common pin.
Advantageously, a single stop is associated with two overhanging arms and is located within the plane of symmetry, or the stop can be divided in two parts symmetrically arranged with respect to the plane of symmetry.
Advantageously, the switching member has an eccentrically arranged journal which engages in a preferably, linear moveable switching element, e.g., a moveable sleeve. A plurality of switching elements can advantageously be connected, at least partially, by switching transmission means, e.g, a switching plate. Advantageously, decoupling of two components of a rotational movement of the rotary switch is effected by displacement of the switching transmission means in two mutually perpendicular directions.
When there are provided three switching elements, a first switching element provides for turning a rotary drive of the tool spindle of the hand-held tool on and off, a second switching element provides for turning a percussion drive of the tool spindle of the hand-held tool on and off, and a third switching element provides for effecting one of blocking a rotational movement of the tool spindle relative to a hand-held tool housing and unblocking the rotational movement of the tool spindle relative to the housing.
At least three operation modes which are selected by a rotary switch upon its incomplete rotation within an angular range of 360xc2x0, are uniformly distributed in the operational range of the rotary switch in accordance with the switching sequence.
The rotary switch insures that more than two operational modes can be switched on or actuated only in a definite sequence. The rotary switch sets an angular region corresponding to respective operational mode and, with an eccentrically arranged member, formlockingly transforms the rotation over the set angular region into a linear movement of a first, axially displaceable switching element which is connected, by a switching transmission means, with a synchronizingly linearly displaceable, second switching element actuatable in another region. Thereby, a user can select, with a rotary switch, one or more than two operational modes of a combination hand-held tool.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to is construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of the preferred embodiment when read with reference to the accompanying drawings.